Chemical Reactions

Q: What happens during a chemical reaction?

A: Bonds are made and broken to form new substances with new properties.

Q: What does the First Law of Thermodynamics state?

A: Energy cannot be created or destroyed, only transformed.

Q: What does the Second Law of Thermodynamics state?

A: Entropy (disorder) in the universe always increases.

Q: What is ΔG (Delta G)?

A: The change in free energy during a reactio

Q: What type of reaction has ΔG < 0?

A: Exergonic (releases energy, spontaneous).

Q: What type of reaction has ΔG > 0?

A: Endergonic (requires energy input, non-spontaneous)

Q: What is reaction coupling?

A: Pairing an endergonic reaction with an exergonic one to make the overall process favorable (ΔG < 0)

Q: What is ATP’s role in the cell?

A: It’s the main energy currency that drives endergonic processes.

Q: How does ATP drive reactions?

A: By transferring its third phosphate group to other molecules (phosphorylation).

Q: Why is ATP hydrolysis highly exergonic?

A: Due to repulsion between negatively charged phosphate groups.

Q: What are enzymes?

A: Biological catalysts (usually proteins) that speed up reactions without being consumed.

Q: What is a substrate?

A: The molecule an enzyme binds and acts upon.

Q: What is the active site?

A: The region of an enzyme where the substrate binds and the reaction occurs.

Q: What is the lock-and-key model?

A: The substrate fits perfectly into the enzyme’s active site

Q: What is the induced fit model?

A: The enzyme slightly changes shape to fit the substrate better.

Q: How do enzymes lower activation energy?

A: By stabilizing the transition state, straining bonds, and orienting atoms properly.

Q: Are enzymes reusable?

A: Yes, they aren’t used up in reactions.

Q: What happens if the temperature or pH is not optimal?

A: Enzymes can denature, losing structure and function.

Q: How are enzymes named?

A: Usually end in “-ase” (e.g., lipase, amylase).

Q: What happens to enzymes at high temperatures?

A: They denature due to disrupted hydrogen bonds.

Q: Why do enzymes have different optimal pH values?

A: Their activity reflects the pH of their normal environment (e.g., stomach = acidic).

Q: What are cofactors?

A: Inorganic ions (e.g., Mg²⁺, Fe²⁺) that help enzyme activity.

Q: What are coenzymes?

A: Organic helper molecules, often derived from vitamins (e.g., NAD⁺, FAD).

Q: Why are vitamins important for enzymes?

A: They help form coenzymes necessary for enzyme function.

Q: What is a competitive inhibitor?

A: A molecule that competes with the substrate for the active site.

Q: What is a non-competitive (allosteric) inhibitor?

A: Binds to another site, changing the enzyme’s shape and reducing activity.

Q: What is feedback inhibition?

A: When the end product of a pathway inhibits an earlier enzyme to prevent overproduction.

Q: What is an irreversible inhibitor?

A: Permanently deactivates an enzyme (e.g., poisons).

Q: What is anabolism?

A: Building larger molecules from smaller ones (uses energy).

Q: What is catabolism?

A: Breaking down larger molecules (releases energy).

Q: What is a metabolic pathway?

A: A series of enzyme-controlled reactions in a sequence.

Q: What is activation energy?

A: The energy needed to start a chemical reaction.

Q: What is denaturation?

A: Loss of an enzyme’s shape and function due to pH or temperature changes.

Q: What is phosphorylation?

A: Adding a phosphate group to a molecule to change its activity.

Q: What is free energy (G)?

A: The energy available in a system to do work.